It could be he's incredibly nervous about anything sexual, or there could be a problem there. talk to him about what he thinks is wrong. Drinking and drugs can effect males to the point of not keeping it up.

Are you rushing into the actual sex part and missing out on the other parts like foreplay? Does he drink or take drugs? Is he getting too overly excited? Is there any pressure? Are you having sex in a place and situation where you can both relax?

Is he a heavy drinker or takes recreational drugs ? This can affect a man's erection. Additionally some medications for high blood pressure can cause problems too. Also some men have psychological problems that can cause erectile dysfunction. Have you talked this over with him?

Well, your question is specific, but vague on details. If you are having sex while intoxicated, that would do it. If you are having sex where you may get caught, that would do it. If you are in a normal setting, and he gets hard, but loses it, it could be that he is conscious of it now, and once that happens, it is difficult to not think of it. I would recommend it that is the case, when he loses his erection, make him feel like you are not bothered, and try to make him feel comfortable..maybe use your hand or mouth, but DON"T just roll over and be silent. He'll feel much better if you help him, kindly, and then it should clear up!

Does he take painkillers? If so that will make him lose it right now!I just started seeing a man that does the same thing and he told me that its because he has been taking painkillers for years,an he only had sex to please me he new it would happen!!